My truck seems to have power going down the road but when I kick it down to climb a hill or pass it just dogs out and only will run about 3000 rpm's. Anyone have a clue to why this is happening?

Maybe fuel pressure. Check for clogged filter.

possibly a plugged catalytic converter

I've seen someone with the same symtoms say
it was thier catalytic converter

I noticed a fairly drastic change in my truck when I replaced my cats. ('97 Vortec C1500) It's a good place to start.